The oilwell industry utilizes borehole-sounding devices to investigate conditions in the drilled borehole. These conditions include well depth and/or the presence or level of water. Present borehole tools are designed to detect either the presence or level of water or measure borehole depth, but not both parameters simultaneously. This is due to design factors associated with these types of tools that prevent use as a combined tool. Two separate borehole loggings are required should both parameters need to be measured.
The cabling to connect most commercial logging tools is a flat, antenna type wire that has delicate insulation and wire conductors. In the harsh conditions existing in boreholes, this insulation often is easily cut or abraded on the well casing joints or on the upper edges of the casing. These harsh conditions can also cause breaking of the wires. In some cases, this wire breakage results in the logging tool being lost down the hole and can require expensive retrieval operations to recover the tool.
With commercial water level sensing tools, leakage is a common problem, allowing water to enter the internal areas of the tool where electrical connections are made. This wetting of the connections can cause the tool to render erroneous readings, and to corrode or otherwise foul the electrical connections. After use, a leaking tool must be disassembled, dried, and then reassembled. Often, the electrical contacts are difficult to reach for cleaning purposes.
Most commercial, bottom-sensing, logging tools use a mechanical sensing switch that, after a period of time, fails due to repeated exposure to water that leaks into the internal spaces of the tool. In addition, the mechanical sensing switch is normally a tight-fitting, sliding, hole-bottom contact that is adversely affected by mud or very dirty water in the borehole.
The present invention provides a multipurpose well-logging tool that provides both water sensing and bottom sensing capabilities in one logging tool. It is capable of performing both functions while overcoming many of the problems associated with other tools of this type.
The present invention provides a watertight borehole tool having sensors for both borehole depth and water presence and level, and replaces individual borehole tools for each function. This results in significant savings in both time and money since a single borehole logging can provide information on several conditions within the borehole.
Additional advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.